1. Technical Field
The present invention relates to a light emitting device and an atomic oscillator.
2. Related Art
In recent years, an atomic oscillator using coherent population trapping (CPT) as a quantum interference effect has been proposed, and downsizing and reduction in power consumption of the device have been expected. The atomic oscillator using CPT uses an electromagnetically induced transparency phenomenon (EIT phenomenon) that absorption of coherent light beams respectively having two wavelengths (frequencies) that are different from each other stops if an alkali metal atom is irradiated with the resonance light beams.
The atomic oscillator can realize high accuracy by accurately controlling the difference (the frequency difference) between the two wavelengths described above. Therefore, it is preferable for a light emitting device (a light source) for emitting light beams respectively having the two wavelengths to have a variable wavelength mechanism for retrieving the wavelengths to predetermined values in the case in which the wavelengths of the light beams emitted from the light emitting device fluctuate due to the temperature of the light emitting device.
For example, JP-A-10-270799 describes a light emitting device provided with a wavelength conversion section for absorbing light emitted by a light emitting section, then converting the light thus absorbed into light with a wavelength based on the magnitude of an external electric field or the presence or absence of the external electric field, and then emitting the result.
However, in the light emitting device of JP-A-10-270799, since the wavelength of the light to be emitted is varied due to the absorption of the light in the wavelength conversion section, the variation in the wavelength is large, and it is difficult to vary the wavelength with a small variation. Therefore, the light emitting device of JP-A-10-270799 cannot control the wavelength with high accuracy, and cannot be used as a light source of the atomic oscillator.